Assessment of temperature and specific humidity inversions and their relationships in three global reanalysis products over the Arctic Ocean

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  • 1 College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China.
  • 2 State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China.
  • 3 Key Laboratory for Polar Science, Polar Research Institute of China, Ministry of Natural Resources, Shanghai 200136, China.
  • 4 College of Marine Ecology and Environment, Shanghai Ocean University, Shanghai 201306, China.
  • 5 Shanghai Engineering Research Center of Estuarine and Oceanographic Mapping, Shanghai 201306, China.
  • 6 Key Laboratory for Information Science of Electromagnetic Waves, Fudan University, Shanghai 200433, China.
  • 7 Southern Marine Science and Engineering, Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
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Abstract

Characteristics of temperature and specific humidity inversions (TIs and SHIs, respectively), and their relationships in three of the latest global reanalyses, the European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-I), the Japanese 55-year Reanalysis (JRA-55) and the ERA-5, are assessed against in-situ radiosonde (RS) measurements from two expeditions over the Arctic Ocean. All reanalyses tend to detect much lower TI and SHI occurrences, together with much less common multiple TIs and SHIs per profile than RS data in summer 2008, winter 2015 and spring 2015. The reanalyses generally well depict the relationships among TI characteristics seen in RS data, except for the TIs below 400 m in summer, as well as above 1000 m in summer and winter. The depth is worst simulated by the reanalyses among the SHI characteristics, which may result from its sensitivity to the uncertainties in specific humidity in the reanalyses. The strongest TI per profile in RS data exhibits more robust dependency on surface conditions than the strongest SHI per profile, and the former is better presented by the reanalyses than the latter. Furthermore, all reanalyses have difficulties simulating the relationships between TIs and SHIs, together with the correlations between the simultaneous inversions. The accuracy and vertical resolution in the reanalyses are both important to properly capture occurrence and characteristics of the Arctic inversions. Generally, ERA-5 performs better than ERA-I and JRA-55 in depicting the relationships among the TIs. However, the representation of SHIs is more challenging than TIs in all reanalyses over the Arctic Ocean.

Corresponding author: Yang Zhang (yzhang@sio.org.cn)

Abstract

Characteristics of temperature and specific humidity inversions (TIs and SHIs, respectively), and their relationships in three of the latest global reanalyses, the European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-I), the Japanese 55-year Reanalysis (JRA-55) and the ERA-5, are assessed against in-situ radiosonde (RS) measurements from two expeditions over the Arctic Ocean. All reanalyses tend to detect much lower TI and SHI occurrences, together with much less common multiple TIs and SHIs per profile than RS data in summer 2008, winter 2015 and spring 2015. The reanalyses generally well depict the relationships among TI characteristics seen in RS data, except for the TIs below 400 m in summer, as well as above 1000 m in summer and winter. The depth is worst simulated by the reanalyses among the SHI characteristics, which may result from its sensitivity to the uncertainties in specific humidity in the reanalyses. The strongest TI per profile in RS data exhibits more robust dependency on surface conditions than the strongest SHI per profile, and the former is better presented by the reanalyses than the latter. Furthermore, all reanalyses have difficulties simulating the relationships between TIs and SHIs, together with the correlations between the simultaneous inversions. The accuracy and vertical resolution in the reanalyses are both important to properly capture occurrence and characteristics of the Arctic inversions. Generally, ERA-5 performs better than ERA-I and JRA-55 in depicting the relationships among the TIs. However, the representation of SHIs is more challenging than TIs in all reanalyses over the Arctic Ocean.

Corresponding author: Yang Zhang (yzhang@sio.org.cn)
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